Technical Field
The present invention relates to a platinum oxide colloidal solution, a manufacturing method therefor, a manufacture apparatus thereof, and a method of injecting a noble metal of a boiling water nuclear power plant.
Background Art
In a boiling water nuclear power plant, it is important from the viewpoint of improving operation rate of the boiling water nuclear power plant to suppress stress corrosion cracking of reactor internals installed in a reactor pressure vessel and pipes (for example, recirculation pipes) connected to the reactor pressure vessel.
Regarding the stress corrosion cracking, the following is known and measures for the stress corrosion cracking are taken. High-temperature and high-pressure cooling water (hereinafter, referred to as reactor water) in contact with the reactor internals, and the pipes connected to the reactor pressure vessel contains oxygen and hydrogen peroxide generated by radiolysis of the reactor water in a core in the reactor pressure vessel. Therefore, the stress corrosion cracking progresses remarkably as the oxygen concentration and hydrogen peroxide concentration in the reactor water increase. The progress of each stress corrosion cracking in the reactor internal and pipes in contact with the reactor water can be suppressed by reducing the oxygen concentration and hydrogen peroxide concentration in the reactor water.
There is noble metal injection as a typical method for suppressing the stress corrosion cracking. The noble metal injection is a technology of injecting a compound of a noble metal (platinum, rhodium, or palladium) into the reactor water, depositing the noble metal on surfaces of the reactor internals and an inner surface of each pipe connected to the reactor pressure vessel, and injecting hydrogen into the reactor water (for example, refer to Japanese Patent Laid-open No. 7(1995)-311296). The noble metal promotes the respective reactions of hydrogen with each of oxygen and hydrogen peroxide and reduces the oxygen concentration and hydrogen peroxide concentration in the reactor water in contact with the surfaces of the reactor internals and the inner surface of each pipe connected to the reactor pressure vessel. Japanese Patent Laid-open No. 7(1995)-311296 describes an acetylacetonate compound of a noble metal and a nitric compound of a noble metal as a noble metal compound to be injected into the reactor water. In Japanese Patent Laid-open No. 7(1995)-311296, a solution with the nitric compound of the noble metal dissolved in water or a solution with the acetylacetonate compound of the noble metal dissolved in alcohol such as ethanol is injected into the reactor water.
On the other hand, although not for the reactor water, in Japanese Patent Laid-open No. 2002-245854, a metal colloidal liquid containing a compound having respectively at least one of an amino group and a carboxyl group is disclosed. Here, gold, silver, copper, platinum, palladium, rhodium, ruthenium, iridium, osmium and others as a metallic component are cited. Further, it is described that light such as UV, an electron beam, and thermal energy may be used for reduction of metallic salt. Furthermore, as a method for washing a solution including metallic colloidal particles, a method of demineralizing by an ultra-filter or an ion exchanger is described.
It is described in Japanese Patent Laid-open No. 2003-215289 that nano particles including a noble metal are injected into the reactor water. In Japanese Patent Laid-open No. 2003-215289, ZnO, Al2O3, or ZrO2 as a neutral active material is used and noble metal nano particles with a noble metal (platinum, palladium, ruthenium, rhodium, osmium, or iridium) adhered on the surface of the neutral active material are injected into the reactor water flowing through the recirculation system connected to the reactor pressure vessel. Hydrogen is injected into the reactor water and the hydrogen and the oxygen contained in the reactor water are reacted to water by the catalytic activity of the noble metal. As a result, the dissolved oxygen concentration in the reactor water is reduced.
Further, Japanese Patent Laid-open No. 2005-10160 describes a method of preventing stress corrosion cracking of structural material. In the method of preventing the stress corrosion cracking, an enriched suspension of catalyst nano particles of a noble metal (for example, platinum) is injected into the reactor water in the reactor pressure vessel through the pipe (for example, a residual heat removal pipe, a recirculation pipe, and a water feed pipe, etc.) connected to the reactor pressure vessel.
The pipes connected to the reactor pressure vessel are made up of stainless steel or carbon steel, so that if any pipe is exposed to high-temperature water, the inner surface (liquid contact surface) of the pipe is covered with an oxide film containing a main component of α-Fe2O3. It is reported that a point of zero charge (pH when the surface potential becomes 0) of α-Fe2O3 is 3.7 to 5.2 at 23° C. and 3.4 at 235° C. (P. Jayaweera et al., Colloids and Surfaces A: Physicochemical and Engineering Aspects, 85, pp. 19-27 (1994)).